The same problem. And Apple won't recognize my iPad with serial and imei. support know nothing about it. I investigate this problem. it can be if your device was in service. if was changed gsm or motherboard. If your device was unbound from locked icloud. And if Aplle just decides to delete your devise from server as my device 🙂 All they have to do this is add your device stats to server again. Only after this your device will held activation. In theory. Information was taken from allot of cervice and different technical supports.